This invention relates to a catalytic hydrocracking process and a catalyst for use therein. More particularly, the invention relates to a hydrocracking catalyst of improved properties for producing gasoline from gas oils and the like under hydrocracking conditions.
Petroleum refiners often produce desirable products such as middle distillate (or midbarrel) products, including turbine fuel and diesel fuel, as well as lower boiling products, such as naphtha and gasoline, by hydrocracking a hydrocarbon feedstock derived from a crude oil. Feedstocks most often subjected to hydrocracking include gas oils recovered as a fraction from a crude oil by distillation by coking and the like. The typical gas oil comprises a substantial proportion of hydrocarbon components boiling above about 400.degree. F., usually at least about 60% by weight boiling above about 500.degree. F.
Hydrocracking is generally accomplished by contacting, in an appropriate reactor vessel, the gas oil or other feedstock to be treated with a suitable hydrocracking catalyst under suitable conditions of elevated temperature and pressure in the presence of hydrogen so as to yield a distribution of hydrocarbon products required by (or satisfactory to) the refiner. Although the operating conditions within a hydrocracking reactor are of obvious importance in influencing the yield of product or products, the hydrocracking catalyst is of vital importance in this regard. Many catalysts are known for hydrocracking, but since their respective catalytic properties vary widely, it can be appreciated that hydrocracking catalysts having great usefulness for one purpose, as for example, for maximizing gasoline and naphtha production, are unsuitable for many other purposes, as for example, maximizing the yield of turbine fuel. And even among catalysts useful for producing the same product, the usefulness of each varies according to the requirements of the refiner. For example, hydrocracking catalysts having high activity for maximum gasoline production under typical hydrocracking conditions have proven inferior for more specific purposes, as for example, where a relatively large yield of gasoline of improved octane quality is desired.
Oftentimes refiners have resorted to using catalysts at relatively severe hydrocracking conditions to obtain sufficient yields of high octane quality gasoline. Also, gasoline octane quality has traditionally been improved with the addition of lead compounds to gasoline; however, recent environmental legislation has restricted such lead addition to the extent that refiners are searching for improved hydrocracking catalysts and processes in order to produce gasoline of high octane, thus minimizing the subsequent addition of octane improvers.
In the search for improved hydrocracking catalysts and processes that produce improved gasoline octane quality, the activity of the hydrocracking catalyst must also be considered. Activity may be determined by comparing the temperature at which various catalysts must be utilized under otherwise constant hydrocracking conditions with the same feedstock so as to produce a given percentage of hydrocarbon products boiling at or below a given temperature or to produce a hydrocarbon product having a given API gravity. The lower the temperature at which the catalyst must be utilized at the given conditions, the more active such a catalyst is for hydrocracking. Alternatively, when various catalysts are utilized under otherwise constant hydrocracking conditions with the same feedstock, activity may be determined by comparing the increase in percentage of hydrocarbon products boiling below a given temperature (for example hydrocarbon products boiling at or less than about 400.degree. F.). The higher the percentage of hydrocarbon product boiling below a given temperature for a given catalyst, the more active such a catalyst is in relation to a catalyst yielding a lower percentage of hydrocarbon product boiling below the same given temperature.
Accordingly, the present invention is directed to a catalyst and catalytic hydrocracking process primarily of advantage in producing a gasoline of improved octane quality, and more particularly, in producing such gasoline without a major sacrifice in activity.
It is a major object of the invention to provide a catalytic hydrocracking process utilizing a hydrocracking catalyst of superior properties for producing a gasoline of improved octane quality from gas oils and the like. A more specific object of the invention is to provide a suitably active catalyst for use in a catalytic hydrocracking process for treating hydrocarbon feedstocks boiling primarily above 400.degree. F. to produce a light and/or a heavy gasoline fraction of improved octane quality. These and other objects of the invention will become more apparent in view of the following description of the invention taken together with the Examples and claims.